ARTICLE Biofilm formation and virulence of uropathogenic Escherichia coli in urine after consumption of cranberry-lingonberry juice T. Tapiainen & H. Jauhiainen & L. Jaakola & J. Salo & J. Sevander & I. Ikäheimo & A. M. Pirttilä & A. Hohtola & M. Uhari Received: 27 April 2011 /Accepted: 11 July 2011 # Springer-Verlag 2011 Abstract Cranberry-lingonberry juice (CLJ) was effec- tive in preventing urinary tract infections (UTIs) in our earlier randomized clinical trial. We aimed to test whether consumption of CLJ at a similar dose to earlier reduces the biofilm formation and virulence of uropa- thogenic Escherichia coli in urine. Twenty healthy women drank 100 ml of CLJ daily for two weeks. Urine samples were obtained 2–4 hours after the last dose. Control samples were taken after a one-week period without berry consumption. Biofilm formation of 20 E. coli strains was measured at 72 hours by the polystyrene microtitre plate method. Quantitative real-time PCR analyses were per- formed for selected genes. Four of the 20 clinical strains produced more biofilm in urine after CLJ consumption (P <0.05) and one produced less. Expression levels of the pga, cpxA, fimA and papF genes did not differ between bacteria grown in control urine and urine obtained after CLJ consumption, except for pga gene expression, which was reduced in one strain after CLJ (P=0.04). It appears that the effect of CLJ in preventing UTIs is not explained by mechanisms that reduce biofilm formation or the expression of selected virulence genes of Escherichia coli in urine. Introduction Urinary tract infections (UTI) result in significant morbidity in young women, as about half have at least one cystitis episode by the age of 35 years [1] and a similar proportion experience recurrent episodes [2]. Cranberry juice has traditionally been used to reduce recurrent UTIs. In two randomized trials, regular consump- tion of cranberry or cranberry-lingonberry juice (CLJ) reduced the occurrence of UTIs by 30–40% in adult women [3–5]. The mechanism of action is not fully understood but it has been suggested cranberry products confer anti- adhesive properties on urine with respect to UPEC (uropathogenic Escherichia coli) strains and uroepithelial cells [6]. It has been suggested recently that recurrent UTI may be caused by Escherichia coli that reside in a dormant, biofilm-like state in intracellular pods in the bladder [7, 8]. Biofilm formation by uropathogenic Escherichia coli (UPEC) in vitro has been shown to correlate with the presence of virulence factors of UPEC strains such as papC and PapG alleles and sfa/focDE [9]. The ability of UPEC strains to form biofilm has been associated with the clinical presentation of UTI, as such strains isolated from patients with pyelonephritis proved to be strong biofilm producers in our previous study [10]. We now used a similar CLJ dose to that which showed good efficacy in preventing UTIs in our earlier clinical trial among young adult women and tested whether urine T. Tapiainen (*) : J. Salo : J. Sevander : M. Uhari Department of Pediatrics, University of Oulu, P.O. Box 5000, 90014 Oulu, Finland e-mail: terhi.tapiainen@oulu.fi H. Jauhiainen : L. Jaakola : A. M. Pirttilä : A. Hohtola Department of Biology, University of Oulu, Oulu, Finland I. Ikäheimo Microbiology Laboratory, Oulu University Hospital, Oulu, Finland Eur J Clin Microbiol Infect Dis DOI 10.1007/s10096-011-1355-2